61809581 has 2 divisors, whose sum is σ = 61809582. Its totient is φ = 61809580.

The previous prime is 61809563. The next prime is 61809593. The reversal of 61809581 is 18590816.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58446025 + 3363556 = 7645^2 + 1834^2 .

It is a cyclic number.

It is not a de Polignac number, because 61809581 - 2¹⁴ = 61793197 is a prime.

It is a super-2 number, since 2×61809581² = 7640848606791122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61809281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30904790 + 30904791.

It is an arithmetic number, because the mean of its divisors is an integer number (30904791).

Almost surely, 2^61809581 is an apocalyptic number.

It is an amenable number.

61809581 is a deficient number, since it is larger than the sum of its proper divisors (1).

61809581 is an equidigital number, since it uses as much as digits as its factorization.

61809581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 38.

The square root of 61809581 is about 7861.9069569666. The cubic root of 61809581 is about 395.3835530945.

The spelling of 61809581 in words is "sixty-one million, eight hundred nine thousand, five hundred eighty-one".